Electrical submersible pumps are commonly used in oil wells for pumping large volumes of fluids. The pump is centrifugal, having a large number of stages of impellers and diffusers. An electrical motor is attached to the pump for driving the pump.
This type of pump is also used for various surface applications, such as for injecting a fluid into the well. In the surface application, the pump is mounted on a skid. An intake chamber is mounted to the intake end of the pump. A thrust chamber having a thrust bearing located therein is mounted to the intake chamber. The electrical motor is mounted to the skid independently of the pump. The shaft of the electrical motor couples to the shaft extending through the thrust chamber.
The typical prior art surface pumps of this type utilize a thrust chamber that is filled with a clean lubricating oil for lubricating the thrust bearing. The working fluid being pumped, typically water, does not enter the thrust portion of the thrust chamber containing the lubricant. While this type of pump works well, the seal between the lubricant and the working fluid in the intake chamber must be replaced from time to time due to wear. This can be a difficult task because it requires removal of the entire thrust bearing assembly from the pump assembly. During removal time, the pump will be shut down and cannot be operated.
U.S. Pat. No. 5,957,656 discloses a surface mounted pump with a thrust chamber that utilizes a filtered portion of the working fluid for lubricating the bearings, rather than a clean lubricant. The thrust chamber mounts to the intake chamber. A line extends from the working fluid intake extends to a separator or filter, and from there to a small pump stage for pumping filtered fluid through the thrust chamber bearings. The filtered fluid then re-enters the intake chamber.